Whatever they say about living in a surveillance society, the standard of snooping in this country clearly leaves much to be desired. It is almost unbelievable that no record exists of Carol Thatcher disgracing herself after The One Show, a scene which, according to the BBC, cannot even be classified as private. Does not an event's non-availability on YouTube constitute one of the last, meaningful definitions of the word?

At the same time video clips refresh one's memory of the Ross/Brand outrage and of Prince Harry's "little Paki friend", BBC functionaries confirm Thatcher's shame of shames rests on a heap of paraphrase, to the effect that she compared a black tennis player to a golliwog. Though, like Gordon Brown's jest about "British Jobs for British Workers", Thatcher insists she didn't meant anything by it.

What else did she say? How much had she drunk? Was this routine behaviour, once her roving reportage was done for the week? Out of the 12 people present, including Jo Brand and Adrian Chiles, it is still not known if all were offended by her observations and equally convinced of their civic duty to report their colleague to the nearest line manager, so as to have her re-educated or removed.

As this feels very much like a test case, where the correct response to racist celebrity asides is concerned, it has to be irrelevant that in the case of The One Show, the outcome is not universally regretted. Younger viewers perhaps fail to grasp just how offensive the words "Carol Thatcher" once were. Long before she was signed up by The One Show, presumably in the belief that her mother was still prime minister, Carol's promotion, within the BBC and outside it, caused real hurt to journalists whose relations were unable to bring similar influence to bear on the Thatcherite meritocracy. Even now, one notices, she has the good fortune to be martyred for being politically incorrect, instead of being sacked 30 years too late, for having no discernible talent.

If this is unfair to Ms Thatcher, we can no doubt leave it to her former producers on The One Show to explain what a noble mind is here o'erthrown. More pressing, surely, is the potential impact of this event on more deserving workers. However justified they might be in believing that Thatcher's staggeringly unpleasant language, like Clarkson's mockery of the one-eyed, or Ross's persecution of OAPs, to be behaviour pretty much exclusive to top BBC celebrities, that is not to say that otherwise decent civilians might not, from time to time, find their inner lives departing from best diversity practice. Even if no one in their right mind would want to defend to the death Carol Thatcher's right to racially insult black tennis players, it is not impossible that her current treatment could one day influence their own.

Some of the finest minds may entertain - though this is obviously hard for many of us to accept - flashes of culturally inappropriate thoughts or language. Making it theoretically possible that one of these thoughts or words might occasionally spill out in circumstances where, despite the apparent informality, others might take offence, either personally or as a proxy for the relevant insulted group. Impossible to imagine? Picture Philip Larkin or TS Eliot on the razzle, before they were exposed, respectively, as a pervert and antisemite.

In the absence of a green room, unacceptable lapses have conventionally occurred in canteens or at office parties where people such as John Prescott toss their secretaries in the air. But as the golliwog-minded die off, and as more and more workers become careful about their language, offensive speech is probably more prevalent in the City, in business and the sequestered spaces of the political class. In Alastair Campbell's diary, we find, for instance, that when they shared office, he and his colleague Tony Blair regularly indulged in blokeish speculation about women. Ubiquitous as he is, Adrian Chiles cannot be expected to police the whole world.

At least, from Campbell, we learn what we did not know during his administration: that Blair's private speech about women was strikingly at odds with Labour's ideals. Do such covert thought crimes matter? Certainly, if you believe BBC 1's controller Jay Hunt. When pressed on Carol Thatcher's right to privacy, she indicated that public/private boundaries do not signify where offensive speech is concerned. "I don't think it's fine that she says this at home," she told the Today programme.

So how, in future, can Ms Hunt control what her staff are saying when they are not on BBC premises? A reliable, Nineteen Eighty-Four-style method for reading minds may still be some way off, but from China to East Germany, real-life thought policemen have proved the effectiveness of friends and lovers, spouses and children, in enforcing domestic conformity with official belief systems. Perhaps the requirement to say nothing at home you would not say at work cannot always be reconciled with freedom of expression, but as the golliwog incident reminds us, that liberty is increasingly trumped by the competing right not to be offended. Even in spirit.

That the BBC expected Thatcher to patrol what passes for her consciousness in a place where the flow of wine indicates that professional expectations have been temporarily suspended makes her case a significant advance on the now routine suppression of unwelcome plays, books, cartoons etc. If, as Ms Hunt suggests, staff who slacken in their self-censorship court public shame, employees will surely want to protect themselves from malicious accusations by insisting on recording equipment in every corner of their workplace.

Of course, an absence of compromising evidence is no guarantee that the inside of your friend or colleague's head is as blameless an environment as Jo Brand's. The corps of the English National Ballet presumably had no idea, until told by newspapers, they had been pirouetting around a BNP member. And think of Mrs Max Mosley: unaware, until the News of the World filmed him at it, that the FIA president, her husband of 48 years, regularly participated in sadomasochistic orgies.

To the consternation of many of us who do not like to think that the figurehead of the Camping and Caravanning Club is a keen user of prostitutes, Mr Justice Eady ruled that there had been no public interest justification for Mosley's exposure, noting that European law "affords respect to an individual's right to conduct his or her personal life without state interference or condemnation". Even among the prostitutes, Mosley had a reasonable expectation of privacy.

Rather reluctantly, given what the case revealed about Mosley, who presumably numbers women among his colleagues, I have come to accept that Eady was right: a man's repellent sexual behaviour in private, if it is not illegal, should not be used to disqualify him from public life. In which case, Thatcher's offensive choice of words, unknown to her audience, surely merits an equally strong defence. Even when she partied with The One Show, she had a reasonable expectation of privacy. And if we can't speak freely in private, we're finished.